Natural products used for ceremonial, religious, or medical purposes and with a history of altering cognition have lead to the discovery of compounds that have been useful as scientific probes of brain function and as treatments in modern medicine. Despite their benefits, some of these compounds, such as cocaine and nicotine, have the potential to be addictive. There is now increased interest in little-known plants believed to have psychoactive properties based on ethnopharmacological information about their religious and ceremonial use. The Internet has made researching and acquiring these plants relatively easy. For many of these plants it is not known if they contain psychoactive compounds and if they do, what their molecular targets are. Thus, these plants are a potential source for interesting compounds affecting brain function. This proposal combines natural products and CNS pharmacological expertise to explore ethnomedical plant leads for new CNS-active compounds. These new compounds can be used to drive pharmacophore development for new probes of CNS function. To accomplish this we will 1) prepare peak libraries from 51 plants with ethnomedical evidence of psychoactivity. 2) Screen these libraries in 96-well plate-based homogeneous functional assays for agonists, antagonist and positive allosteric modulators of human receptors linked to hallucinations (5-HT2A and kappa opioid) and abuse potential (dopamine transporter, cannabinoid 1 and mu opioid). We will also include the novel target, human trace amine associated receptor 1, which is activated by known hallucinogens. 3) Prioritize the samples that hit based on their receptor profile. 4) Use bioactivity-directed fractionation to isolate the active principles from these hits. 5) Determine the structures of the active compounds. 6) Pharmacologically characterize (e.g., EC50 and Emax) these compounds. In addition to finding unique compounds to probe brain function, the data obtained on this project could be used to identify plants that have the potential to be abused. The National Institute on Drug Abuse (NIDA) has recognized a growing trend in the use of these psychoactive plants. Accordingly, NIDA has issued a Program Announcement (PA) [Psychopharmacology of Widely Available Psychoactive Natural Products;PA-04- 084] to stimulate research on these plants. A major goal of this PA is to identify novel CNS-active compounds for use as probes of the CNS function, scaffolds for new CNS- active drug leads, or both. A natural outcome of this work is that the information on the molecular targets of the active compounds in these plants can be used to estimate their abuse potential so that efforts can be undertaken to monitor or limit their availability. Our R21 proposal will address the aims of this PA via an investigation of plants that: 1) are currently used in ethnomedicine or recreationally for their psychoactive properties, especially those causing hallucinations, 2) are readily researched and procured via the Internet, but 3) have not had the CNS targets of their active principles identified. The immediate goal of this R21 grant is to identify novel CNS-active compounds or identify the CNS molecular targets of known compounds from plants believe to contain psychoactive compounds. The long-range goal is to use these data to support submission of RO1 applications that focus on the use of medicinal chemistry to develop probes of CNS function and pharmacological methods to study effect of novel compounds on CNS function. Moreover, these data could be used by NIDA to identify plants with abuse potential.